The present invention relates to a process for producing purified synthesis gas from a soot-containing synthesis gas.
Processes for purifying synthesis gas are known in the art. For example, WO-A-2009/06841 discloses a process for purifying synthesis gas prepared by partial oxidation of a carbonaceous feedstock by mixing the synthesis gas produced with methanol, cooling the resulting mixture, separating a liquid water-methanol mixture from the cooled synthesis and contacting the cooled synthesis gas with methanol to decrease the content of hydrogen sulphide and carbon dioxide. At least part of the methanol used is regenerated and re-used in the process.
US-2009/0152208-A1 discloses a process for treating process water streams generated by a hydrocarbon gasification process, so that the water can be reused. As an important source of the water to be treated US-2009/0152208-A1 mentions the cooling of hot synthesis gas from a gasification process. The cooling method disclosed involves first and second stage cooling with solids removal inbetween. First stage cooling is typically achieved by non-contact heat exchange to a temperature below the dew point of the synthesis gas, thereby condensing part of the water present in the synthesis gas. Contaminants present in the synthesis gas (e.g. hydrogen sulphide, hydrogen chloride, ammonia, dissolved hydrocarbons) are absorbed into the condensate. The condensate is removed as a separate stream from the first stage cooling for further treatment, whilst the cooled synthesis gas is passed into a particulate removal system for removing any soot present. The soot-free synthesis gas subsequently flowing from the particulate removal system is passed into the second stage cooling. This second stage cooling takes place by direct cooling methods, such as quenching or scrubbing with water. The used contact cooling water is suitably combined with the condensate from the first stage cooling for further treatment. Any soot present in the synthesis gas is removed in a particulate removal system located between first and second stage cooling.
The present invention aims to provide an improved process for producing purified synthesis gas from a soot-containing synthesis gas.